Circuit breaker with improved thermal and electromagnetic trip means



March 14, 1967 E. J. WALKER CIRCUIT BREAKER WITH IMPROVED THERMAL ANDELECTROMAGNETIC TRIP MEANS Filed May 24, 1965 INVENTOR Eugene J. WalkerBY 75%;, A. W

ATTORNEY United States Patent Ofitice 3,309,635 Patented Mar. 14, 19673,309,635 CIRCUIT BREAKER WITH HVIPROVED THERMAL AND ELECTROMAGNETICTRIP MEANS Eugene J. Walker, Borough Township, Beaver, Pa., as-

signor to Westinghouse Electric Corporation, Pittsburgh, Pa., acorporation of Pennsylvania Filed May 24, 1965, Ser. No. 458,248 8Claims. (Cl. 335-35) This invention relates generally to circuitbreakers and more particularly to circuit breakers of the typecomprising therinal-and-magnetic trip means.

An object of this invention is to provide a circuit breaker embodying animproved thermal-and-magnetic trip device.

Another object of this invention is to provide a circuit breakercomprising an improved thermal-and-magnetic trip device of the typecomprising an indirectly heated tripping bimetal.

It is old in the art to provide a circuit breaker with athermal-and-magnetic trip device comprising a bimetal that is movableduring thermal tripping operations to trip the breaker, which bimetalsupports one magnetic member of an electromagnet that operates upon theoccurrence of severe overload surrents to magnetically flex the bimetalmember into a tripping position. This type of trip device is described,for example, in the patent to Walker et al., Patent No. 2,892,054. Inthe circuit breaker described in the above-mentioned Walker et 211.,patent, the magnetic air gap between the magnet members of theelectromagnet diminishes as the bimetal flexes toward a trippingposition so that it is possible to have a combinationthermal-and-magnetic tripping operation wherein the bimetal starts toflex upon the occurrence of low overload currents during which flexingmovement the magnetic air gap is decreased to such a dimension that themagnet force serves to complete the tripping operation. For certaininstallations, it is desirable to provide a compact thermal-and-magnetictrip device wherein the magnetic air gap is not decreased as the bimetalflexes toward the tripping position.

Accordingly, another object of this invention is to provide an improvedcircuit breaker having a compact thermal-and-magnetic trip device thatcomprises'an electromagnet trip comprising one member that fiexes uponthe occurence of severe overloads to effect a magnetic trippingoperation in which one member supports a bimetalmember that flexesindependently of the one member upon the occurrence of lesser overloadsto effect a thermal tripping operation. 1

Another object of this invention is to provide a circuit breakerembodying an improved ambient-temperature compensating trip device.

The invention, both as to structure and operation, together withadditional objects and advantages thereof, will be best understood fromthe following detailed description when read in conjunction with theaccompanying drawing.

In said drawing:

FIGURE 1 is a vertical sectional view through the center pole of athree-pole circuit breaker embodying the principles of this invention;

FIGURE 2 is a partial side elevational view of the thermal-and-magnetictrip device seen in FIG. 1; and

FIGURE 3 is a top View of the parts of the thermaland-magnetic tripdevice seen in FIG. 2. g

The invention is illustrated as applied to a circuit breaker of the typedisclosed in the patent to E. J. Walker et al., Patent No. 2,892,054,issued June 23, 1959.

The circuit breaker is of the three-pole type, only one pole beingshown, and it comprises a base 11 and a cover 13 both of moldedinsulating material. A stationary contact 15 and a cooperating movablecontact 17 are provided for each pole of the breaker. An operatingmechanism 19 common to all of the poles is diposed in the center polecompartment (FIG. 1) and each pole is provided with a trip deviceindicated generally at 21.

The stationary contact 15 for each pole of the breaker is rigidlymounted on the inner end of a conducting strip 23. The outer end of thestrip 23 is secured by means of a line terminal connector 25to a metalinsert molded in the base 11. The movable contact 17 'for each of thepoles is mounted on a separate contact arm 27 whichis pivotally mountedby means of a pin 29 on a switch arm 31. The switch arm 31 for theseveral poles are secured to an insulating tie bar 35 which is pivotallysupported in brackets (not shown) by means of pins 37 in the ends of thetie bar. Springs 34 bias the contact arms 27 clockwise about the pins 29to provide contact pressure in the closed position of the switch arms.

The operating mechanism 19 is disposed in the center pole. The mechanism19 comprises a U-shaped operating lever 41 having its inner ends pivotedin V-shaped notches 43 in a pair of spaced metal frame members 45 thatare suitably mounted on the base 11.

The operating lever 41 has an arcuate shield 47 mounted on the outer endthereof. A handle portion 49 extends out from the shield 47 through anopening 51 in the cover 13. The switch arm 31 for the center pole isoperatively connected, by means of a toggle comprising links 53 and 55,to a releasable member or cradle 57 that is pivotally mounted on a pin59 that is supported in the frames 45. The toggle links 53 and arepivotally connected together by a knee pivot pin 61. The toggle link 53ispivotally connected to the releasable cradle 57 by a pivot pin 63 andthe toggle link 55 is pivotally connected by a pin 65 to the switch arm31 for the center pole.

Overcenter springs 67 are connected under tension be-; tween the kneepivot pin 61 of the toggle 53, '55 and the yoke portion of the operatinglever 41.

The contacts for all of the poles are manually opened and closed in awell known manner by movement of the operating lever 41 to the ofposition and then back to the on position. Movement of the lever 41 tothe oil position causes collapse of the toggle 53, 55 and opening of thecontacts 15, 17. During this opening 1 operation, the tie bar 35 isrotated in a counterclockwise (FIG. 1) direction to simultaneously moveall of the contacts 17 to the open position. Reverse movement of thehandle back to the on position causes straightening of the toggle 53, 55and closing of the contacts 15, 17. During the closing operation, thetie bar 35 is rotated in a clockwise (FIG. 1) direction tosimultaneously move all of the contacts 17 to the closed (FIG. 1)position.

The contacts are opened automatically in response to a tripping overloadin any pole of the breaker, by release of the releasable cradle 57. Thecradle is normally releasably restrained in operative position by meansof a latch mechanism indicated generally at 71. The latch mechanism isactuated by the trip device 21 to release the cradle 57. When released,the cradle 57 rotates clockwise about its pivot 59 under the influenceof the Overcenter springs 67 causing collapse of the toggle 53, 55 andopening movement of the switch arms 31.

The latch mechanism comprises a main latch 73 pivoted on a pin 75 in theframe 45 and biased by a spring 77 in unlatching direction. The mainlatch 73 is provided with a latching portion 79 that engages a latch tip81 on the free or latching end of the cradle 57 to releasably hold thecradle in operative position. The latch tip 81 is in-turned and facesgenerally in the direction toward the pivot 59 about which the cradlemoves. The latch 73 is of the slip-off type and is releasably held inlatching position by a light-load cylindrical latch which comprises arotary shaft 83 pivotally mounted in the frame 45 and having a cutoutportion 85. The shaft 83, at a surface adjacent the cutout portion 85,engages a shoulder on the main latch 73. The latch 83 has an upwardlyextending arm 89 secured thereto which, at its upper end, has an ear 91formed thereon. An adjusting screw 93 is threaded into the car 91 and ismovable into engagement with a projection 97 on a trip bar 99. A spring95 biases the arm 89 and the rotary shaft 33 to the latching positionwhere the arm 09 is stopped by engagement of the screw 93 with theprojection 97 on the trip bar.

The trip bar 99 is of molded insulating material and the projection 97is molded integral therewith. The trip bar 99 is pivotally supported bymeans of pins 101 molded in the ends thereof which pins are supported inbrackets (not shown) in the end poles of the breaker adjacent thesidewalls of the housing. The trip bar 99 is provided with a downwardlyextending projection 105 for each pole on which is rigidly mounted anambient temperature compensating bimetal element 107 that is adapted tobe mechanically actuated by the trip device 21 to operate the trip bar99.

The trip device 21 comprises a generally L-shaped heater member 111 anda generally L-shaped magnet member 113. The members 111 and 113 aremounted on the base 11 by means of a screw 115 that passes throughsuitable openings in the horizontal (FIG. 1) legs of the members 111,113 and that is threaded into a metallic insert 117. The insert 117 isfixedly mounted on the base 111 and is provided with a tapped openingtherein for receiving the screw 115. The member 113 is a magneticallypermeable member that serves as one of two magnetically permeablemembers that cooperate to form an electromagnet. The member 111 is aconductor that is connected in the circuit of the breaker. The member111 is connected to a conductor 121 by means of the screw 115 whichfastens these mmebers together. The conductor 121 is a generallyL-shaped member and it is connected to the contact arm 27 ofthe-associated pole by means of a plurality of flexible conductors 123.The conductors 123 are connected at one end thereof to the contact arm27 and at the other end thereof to a flag portion 125 of the conductor121. The upper end of the heater member 111 is connected to a conductor129 that is connected to a terminal conductor 131. The terminalconductor 131 extends out through an opening in the insulating housing,and a terminal connecting screw structure 135 is provided to enableconnection of the terminal conductor 131 to a conducting line.

A tripping bimetal 139 is secured at the lower end thereof to a lowerportion of the heater member 111 by means of a rivet 141. The trippingbimetal 131 is an elongated generally flat member that extends upwardalong one side of the elongated generally flat heater member 111. Thetripping bimetal 139 passes between the legs of a generally U-shapedmagnet member 145 that is secured at the bight portion thereof to themember 111. As can be seen in FIGS. 1-3 the legs of the magnet member145 extend toward the magnet member 113. Each of the magnet members 145and 113 comprises a member of magnetically permeable material such assoft iron. An adjusting screw structure 149 is mounted on the upper orfree end of the tripping bimetal 139. The adjusting screw structure 149is rotatable in order to adjust the dimension of the gap between theadjusting screw structure 149 and the compensating bimetal 107.

The high expansion sides of the compensating bimetal 107 and trippingbimetal 139 are on the left as seen in FIG. 1 and both of these bimetalelements will deflect to the right (FIG. 1) in response to changes inambient temperature whereby the compensating bimetal element 107 willcompensate for deflection of the tripping bimetal 139 in response tochanges in the ambient temperature. It is to be noted that the trippingbimetal 139 is disposed between the heater 111 and the compensatingbimetal 107. It is also to be noted that the magnet member 113 is alsopositioned between the heater 111 and compensating bimetal 107. Thus,the tripping bimetal 139 and also the magnet member 113 serve to shieldthe compensating bimetal 107 from the heat of the heater member 111.

When a low persistent thermal tripping overload current such, forexample, as of the rated current occurs, the bimetal element 139 isheated by a means of the heat generated in the current-carrying heatermember 111, and the bimetal 139 deflects to the right (FIG. 1) to tripthe circuit breaker after a time delay. This tripping movement of thetripping metal 139 operates through the engagement of the adjustingscrew structure 149 and compensating bimetal 107 to rotate the trip bar99 in a clockwise (FIG. 1) direction during which movement theprojection 97 on the trip bar 99 operates against the screw 93 to rotatethe latch member 89 in a clockwise direction to free the main latch 73.The main latch 73 is free when a shoulder portion thereof snaps into thenotch of opening 85 in the shaft 83. The latching point of the mainlatch 73 and the latch portion 81 of the cradle 57 are to the left ofthe pivot 75 so that the main latch 73 is biased in an unlatchingdirection by a component of the force exerted by the overcenter springs67 as well as by means of the torsion spring 77. When the main latch 73is released by the light load trigger latch 83, the main latch isimmediately snapped to the unlatching position releasing the cradle orreleasable member 57 to effect opening of the contacts 15, 17 in thesame manner hereinbefore described. It is noted that during the flexingmovement of the tripping bimetal 139, the tripping'bimetal 139 movesindependent of the heater member 111 and magnet member so that duringthe thermal flexing movement of the bimetal 139 the air gap between themagnet members 145, 113 is not diminished. The bimetal 139 is supportedon and disposed adjacent the current conducting heater member 111 to beheated by means of the heat generated in the heater member 111. The heatfrom the heater member 111 is conducted to the tripping bimetal 139 atthe lower part of the tripping bimetal 139 because of the lower part ofthe tripping bimetal 139 is supported on the heater member 111 in heatconducting engagement with the lower part 153 of the heater member 111.The heat from the heater member 111 is also radiated to the upper part155 of the bimetal 139 through the air gap between the heater member 111and the upper part 155 of the bimetal 139.

Upon the occurrence of an automatic tripping operation, the force of theovercenter springs 67 operates to move the operating handle 49 to atripped position intermediate the on and off positions in a manner wellknown in the art to provide a visual indication that the circuit breakerhas been tripped. Before the contacts can be closed following a trippingor automatic opening operation, it is necessary to reset and relatch themechanism. This is accomplished by moving the handle 49 t0 the full offposition. During this movement, a projection 159 on the operating lever41 engages a shoulder 161 on the cradle .or releasable member 57 to movethe cradle 57 in a counterclockwise resetting direction about the pivot59. Near the end of this movement, the lower rounded portion of thelatch end 81 of the cradle 57 engages the outwardly extending arm of thebell-crank shaped latch member 73 to move the latch member 73 to thelatching position. As soon as the shoulder (not shown) of the latch 73clears the corner of the notch 85 of the latch 83, the torsion spring 95restores the arm 89 and shaft 83 to the normal latching position. Thelatching portion 79 of the latch 73 is then above the latch 81 and uponrelease of the handle 49 the latch '81 Upon the occurrence of a severeor magnetiotripping overload such, for example, as ten times the normalrated current, the electromagnet 111, 145, 113 is energized by means ofthe current flowing through the member 111 and, therefore, throughthelegs of the U-shaped magnet mmeber 145, to effect an instantaneousmagnetic tripping operation. The magnet member 113 is stiff relative tothe heater member 111 so that when the electromagnet is energizedsufficiently to effect a magnetic tripping operation the magnet member145 is attracted to the stationary stiff magnet member 113 flexing theheater member 111 to move the heater member 111 to the right (FIG. 1) toa tripping position. This tripping movement of the heater member 111moves the bimetal 113 that is mounted on the right-hand side (FIG. 1) ofthe heater member 111 whereupon the adjusting screw structure 149 on thebimetal 139 engages the compensating bimetal 107 to rotate the trip bar99 to effect a tripping operation in the same manner as was hereinbeforeset forth with regard to the thermal-tripping operation.

The magnetic tripping operations occur instantaneously upon theoccurrence of a severe overload'or short circuit such, for example, asacurrent often or more times the normal ratedcurrent of the circuitbreaker. The thermal tripping operations, which occur upon theoccurrence of certain overloads below the overload that will effect amagnetic tripping operation, occur with a time-delay so that in somesituations when the overload current condition is a temporary conditionthat will not damage the parts of the protected circuit, the circuitbreaker will not trip. The thermal tripping operations will occur whenthe lesser overloads are persistent enough to last through thetime-delay tripping movement of the tripping bimetal Thethermal-and-magnetic trip device 21 comprises a compact trip device thatis readily mounted in position by means of the mounting screw 115 thatmounts the members 111, 113 and 121 on the base 11 of the circuitbreaker. The tripping bimetal 139 is heated by means of the heatgenerated in the conducting heater member 111. When heated suflicientlythe tripping bimetal flexes, Without diminishing the magnetic air gap ofthe electromagnet trip structure, to effect a thermal trippingoperation. Upon the occurrence of severe overloads the heater member isflexed to move the tripping bimetal to effect a magnetic trippingoperation. The compact thermal-and-magnetic trip device is used in acombination wherein the tripping bimetal and one magnetic member aredisposed between the heater member and a compensating bimetal to shieldthe compensating bimetal from the heat generated in the heater member.The thermal-and-magnetic trip device is a simplified structure that iseasily assembled in that the one magnetic member and bimetal can befixedly assembled on the heater member outside of the circuit breakerhousing, and this assembled structure can be readily mounted in thecircuit breaker along with the other magnetic member by means of a screwthat also serves to connect the heater member in the circuit of thebreaker.

While the invention has been disclosed in accordance with the provisionsof the patent statutes, it is to be understood that various changes inthe structural details and arrangement of parts thereof may be madewithout departing from the spirit of the invention.

I claim as my invention:

1. A circuit breaker comprising a pair of contacts and means releasableto effect opening of said contacts to thereby eifect opening of acircuit, trip means comprising a movable current-carrying heater memberconnected in said circuit, a bimetal member supported to be heated bythe heat generated in said heater member, upon the occurrence of certainoverload current conditions below a predetermined value in said circuitsaid bimetal member flexing independent of movement of said heatermember to effect release of said releasable means, means operativelyconnecting said heater member with said himetal member such thatoperative movement of said heater member operatively moves said bimetalmemben an electromagnet comprisinga stationary magnet member and amovable magnet member, said stationary and movable magnet members beingsupported to be energized by the current in said circuit, meansoperatively connecting said movable magnet member with said heatermember such that operative movement of said movable magnet memberoperatively moves said heater member, and upon the occurence of anoverload current above said predetermined value said movable magnetmember being magnetically attracted toward said stationary magnet memberand moving toward said stationary magnet member to operatively move saidheater member which operative movement of said heater member operativelymoves said bimetal member to effect release of said releasable means.

2. A circuit breaker comprising a pair of contacts and. means releasableto effect opening of said contacts to thereby efiect opening of acircuit, trip means comprising a movable current-carrying heater memberconnected in said circuit, an electromagnet comprisinga first magnetmember and a second magnet 'member, one of said first and second magnetmembers being mounted on said heater member, the other of said first andsecond magnet members being supported in proximity to said one magnetmember, upon the occurrence of an overload current above a predeterminedvalue in said circuit said electromagnet being energized to such anextent by the current in said heater member that said one magnet memberis moved toward said other magnet member, which movement of said onemagnet member operates to move said heater member to thereby effectrelease of said releasable means, a bimetal member supported to beheated by the heat generated in said heater member, upon the occurrenceof certain overload current conditions below said predetermined valuesaid bimetal member being heated sufficiently to flex and moveindependent of movement of said heater member to effect release of saidreleasable means.

3. A circuit breaker comprising a pair of contacts and means releasableto effect opening of said contacts to thereby effect opening of acircuit, trip means comprising an elongated movable current-carryingheater member connected in said circuit, an elongated bimetal membersupported at one end thereof on said elongated heater member andextending alongside said elongated heater member to be heated by theheat generated in said heater member, upon the occurrence of certaincurrent .conditions below a predetermined value said bimetal memberbeing heated sufficiently to flex to move independent of said heatermember to effect release of said releasable means, an electromagnetcomprising a stationary magnet member and a movable magnet member, saidstationary and movable magnet members being supported to be magneticallyenergized by the current in said circuit, means operatively connectingsaid movable magnet member with said heater member such that operativemovement of .said movable magnet member operatively moves said heatermember, and upon the occurrence of an overload current above saidpredetermined value said movable magnet member being magneticallyattracted toward said stationary magnet member and moving toward saidstationary magnet member during which movement said movable magnetmember opera tively moves said heater member to move said bimetal memberthat is supported on said heater member to thereby effect release ofsaid releasable meansthrough said movement of said bimetal member.

4. A circuit breaker comprising'a pair of contacts and means releasableto eflect opening of said contacts to thereby effect opening of acircuit, trip means comprising an elongated current-carrying flexibleheater member connected in said circuit, an electromagnet comprising afirst magnet member and a second magnet member, one of said first andsecond magnet members comprising a generally U-shaped magnet membersupported on said heater member with said heater member being positionedbetween the legs of said U-shaped magnet member, the other of saidmagnet members being supported in proximity to the free ends of the legsof said U-shaped magnet member, upon the occurrence of. an overloadcurrent above a predetermined value in said circuit said electromagnetbeing energized suificiently to effect movement of said U-shaped magnetmember toward said other magnet member whereupon said movement of saidU-shaped magnet member flexes said heater member to move said heatermember to a tripping position to eflfect release of said releasablemeans, an elongated bimetal member supported at one end thereof on saidheater member and extending alongside said heater member, upon theoccurrence of certain overload current conditions "below saidpredetermined value said bimetal member being heated andflexing'independent of movement of said heater member to effect releaseof said releasable means.

5. A circuit breaker comprising a pair ofcontacts and means relasable toeffect opening of said cont=acts,,a trip member operatively movable toeffect release of said releasable means, tn'p means comprising anelongated current-carrying flexible heater member connected in thecircuit of said circuit breaker, an electromagnet comprising a firstmagnet membersupported on said heater member and a second magnet membersupported in proximity to said first magnet member, an elongated bimetalmember supported on said heater member and being positioned between saidheater member and said other magnet member, upon the occurrence ofcertain lesser overload conditions said bimetal member being heated andflexing independent of movement of said heatermember to operatively movesaid trip member, and upon the occurrence of certain overload conditionsof a greater magnitude said electromagnet being energized sufficientlyto move said first magnet member toward said other magnet member whichmovement flexes said heater member to thereby move said bimetal memberto operatively move said trip member.

6. A circuit breaker comprising 'an insulating housing comprising abase, a circuit-breaker mechanism supported within said housing, saidcircuit-breaker mechanism comprising a pair of contacts and meansreleasable to effect opening of said contacts to thereby effect openingof a circuit, a trip member operatively movable to effect release ofsaid releasable means, a thermal'andmagnetic trip device comprising agenerally L-shaped conducting heater member connected in said circuit,said heater member comprising a horizontalleg and a flexible verticalleg, an electromagnet comprising a first magnet member and a secondmagnet member, one of said first and second magnet members being mountedon the vertical leg of said heater member, the other of said magnetmembers comprising a generally L-shaped magnet member comprising agenerally horizontal leg and a generally vertical leg, said other ofsaid magnet members being mounted with the generally vertical legthereof being adjacent said one magnet member, a mounting screw mountingsaid other magnet member and said heater member in said circuit breakerbysecuring the generally horizontal legs thereof one over the other tosaid base, a

terminal conductor connecting said heater member in the said circuit andbeing connected to said heater member by means of said mounting screw,an elongated bimetal member supported at one end thereof on the flexiblevertical leg of said heater member and extending alongside the flexiblevertical leg of said heater member between said heater member and thevertical leg of said other magnet member, an actuator supported on thefree end of said bimetal member, upon the occurrence of certain overloadcurrent conditions below a predetermined amount in said circuit saidheater member being heated to heat said bimetal member and said bimetalmember flexing to a tripping position wherein said actuator operativelymoves said trip member, said flexing of said bimetal member occurringindependent of movement of said heater member, upon the occurrence ofcertain overload current conditions above a predetermined value saidelectromagnet being energized such that said one magnet member isattracted to said other magnet member and said flexible vertical leg ofsaid heater member flexes to permit movement of said one magnet membertoward said other magnet member during which flexing movement of saidflexible vertical leg of said heater member said bimetal member iscarried to a tripped position wherein said actuator engages said tripmember to operatively move said trip member.

7. A circuit breaker comprising an insulating housing and acircuit-braker mechanism supported within said housing, saidcircuit-breaker mechanism comprising a pair of contacts and meansreleasable to efiect opening of said contacts, a trip structuresupported in said housing and comprising a vpivotally supported trip barand an elongated compensating bimetal member supported at one endthereof on said trip bar, said trip structure being operatively movableto effect release of said releasable means, a thermal-and-magnetic tripdevice comprising a generally L-shaped heater member comprising aflexible vertical leg and a horizontal leg, said trip device comprisinga generally L-shaped magnet member comprising a vertical leg and ahorizontal leg, at fastening member fastening the horizontal'leg of saidheater member and the horizontal leg of said L-shaped magnet member tosaid housing, a generally U-shaped magnet member supported on theflexible vertical leg of said heater member with the flexible verticalleg of said heater member extending between the legs of said generallyU-shaped magnet member, the legs of said generally U-shaped magnetmember extending generally toward the vertical leg of said generallyL-shaped magnet member, an elongated tripping bimetal member supportedat one end thereof at the lower end of said flexible vertical leg ofsaid heater member and extending vertically along side said flexiblevertical leg of said heater member between said flexible vertical leg ofsaid heater member and said vertical leg of said generally L-shapedmagnet member, an actuating part on the upper 'free end of said trippingbimetal member, said actuating part being disposed adjacent the upperend of said compensating bimetal member, said thermaland-magnetic tripdevice being supported such that said vertical leg of said generallyL-shaped magnet member and said tripping bimetal member are disposedbetween said compensating bimetal member and said flexible vertical legof said heater member, upon the occurrence of certain overload currentconditions below a predetermined value the heat generated in said heatermember heating said bimetal member and said bimetal member flexing suchthat said actuating part actuates said compensating bimetal member tooperatively move said trip structure, and upon the occurrence of certainoverload current conditions above said predetermined value saidelectromagnet being energized such that said generally U-shaped magnetmember is attracted to the vertical leg of said generally L-shapedmagnet member and said flexible vertical leg of said heater member isflexed by the for e Of. said attraction such that said flexiblevertical- 9 10 leg of said heater member moves to move saidbimetalReferences Cited by the Examiner member to a position wherein saidactuating part actuates UNITED STATES PATENTS sa d compensatlng bunetalmember to operatrvely move 2,892,054 6/1959 Walker et aL 20G 88 saidtrip structure.

, 85,792 1965 B t 1. 200-88 X S. A circuit breaker according to claim 7,and said 5 3 1 5/ uys e a actuating part on the upper free end of saidtripping bi- BERNARD A. GILHEANY, Primary Examiner.

metal member comprising an adjusting screw. R. N. ENVALL, JR., AssistantExaminer.

1. A CIRCUIT BREAKER COMPRISING A PAIR OF CONTACTS AND MEANS RELEASABLETO EFFECT OPENING OF SAID CONTACTS TO THEREBY EFFECT OPENING OF ACIRCUIT, TRIP MEANS COMPRISING A MOVABLE CURRENT-CARRYING HEATER MEMBERCONNECTED IN SAID CIRCUIT, A BIMETAL MEMBER SUPPORTED TO BE HEATED BYTHE HEAT GENERATED IN SAID HEATER MEMBER, UPON THE OCCURRENCE OF CERTAINOVERLOAD CURRENT CONDITIONS BELOW A PREDETERMINED VALUE IN SAID CIRCUITSAID BIMETAL MEMBER FLEXING INDEPENDENT OF MOVEMENT OF SAID HEATERMEMBER TO EFFECT RELEASE OF SAID RELEASABLE MEANS, MEANS OPERATIVELYCONNECTING SAID HEATER MEMBER WITH SAID BIMETAL MEMBER SUCH THATOPERATIVE MOVEMENT OF SAID HEATER MEMBER OPERATIVELY MOVES SAID BIMETALMEMBER, AN ELECTROMAGNET COMPRISING A STATIONARY MAGNET MEMBER AND AMOVABLE MAGNET MEMBER, SAID STATIONARY AND MOVABLE MAGNET MEMBERS BEINGSUPPORTED TO BE ENERGIZED BY THE CURRENT IN SAID CIRUIT, MEANSOPERATIVELY CONNECTING SAID MOVABLE MAGNET MEMBER WITH SAID HEATERMEMBER SUCH THAT OPERATIVE MOVEMENT OF SAID MOVABLE MAGNET MEMBEROPERATIVELY MOVES SAID HEATER MEMBER, AND UPON THE OCCURENCE OF ANOVERLOAD CURRENT ABOVE SAID PREDETERMINED VALUE SAID MOVABLE MAGNETMEMBER BEING MAGNETICALLY ATTRACTED TOWARD SAID STATIONARY MAGNET MEMBERAND MOVING TOWARD SAID STATIONARY MAGNET MEMBER TO OPERATIVELY MOVE SAIDHEATER MEMBER WHICH OPERATIVE MOVEMENT OF SAID HEATER MEMBER OPERATIVELYMOVES SAID BIMETAL MEMBER TO EFFECT RELEASE OF SAID RELEASABLE MEANS.